Ice-laden tree limbs that were felled or snapped clean off blocked several roads and knocked utility lines down, causing power outages and traffic detours throughout the county, police said.

Some 28,000 customers in Sussex County have been without power now for several hours, and electricity may not be fully restored until Thursday morning, said Jersey Central Power & Light spokesman Stan Prater.

"We're seeing tree limbs continue to snap and wires continue to fall," Prater said. We're looking at restoration (of electricity) sometime around tomorrow morning. At this point we're telling people sometime tomorrow morning, and that's the best guess."

Sussex County is being hit the hardest because temperatures are hovering around 31 degrees, or just below freezing, causing ice to build up on trees and wires, Prater said. Elsewhere in the state to the south, temperatures have remained above freezing, Prater said.

The hardest-hit areas in Sussex are Newton, Lafayette, Sparta, Sussex Borough and Branchville.

"This is it - this is where it got impacted the most," Prater said.

Jersey Central Power & Light has more than 60 line crews and 60 tree crews out in the county working to remove trees and restore utility lines, Prater said.

Roads in Sussex that have been affected by closures have included sections of major arteries of Routes 206 in Sandyston and Frankford, Route 15 in Sparta and Lafayette, Route 94 in Hardyston, and Route 519 in Frankford and Hampton.

On top of all that, heavy rains also are causing street and road flooding.

The state Office of Emergency Management issued a press release this afternoon urging northern and central New Jersey drivers to be on the lookout for minor flooding known as "ponding" and the onset of "black ice" during commutes tonight and Thursday morning.

"Both ponding and black ice can be very deceptive and in most cases undetected by the naked eye," the office said. The OEM and state DOT are closely monitoring the highways and salting and treating road surfaces to alleviate the threat of hazardous conditions, the office stated.